REPORT ON CHEMISTRY. 
447 
Chemical formulae have not hitherto obtained much favour in 
England, but the state of the science makes their adoption now 
imperative, and Dr. Turner has with much judgement introduced 
them into the latter half of the fourth edition of his Chemistry . 
Part II.—1. Inorganic Chemistry . 
Physical relations of the gases .—Dobereiner first observed 
the curious fact, that when a receiver having a crack in its 
upper part is filled with hydrogen gas, and placed over water 
in a pneumatic trough, the gas slowly escapes by the fissure, 
while the water rises sometimes to the height of three inches. 
Magnus * * * § explained the phenomenon by supposing the crack 
to absorb and condense the gas, as a porous body does; the 
hydrogen again evaporating from the external surface as it 
comes in contact with the atmosphere. This explanation he 
strengthened by showing, that if an open tube be closed at one 
end by a piece of bladder, be then filled with water, inverted 
over mercury and left at rest, the water escapes by evaporation 
from the external surface of the bladder, and the mercury rises 
in the tube. 
Mr. Graham, in a paper on the Diffusion of Gases f, in 
which he confirmed the previous observations of Dr. Dalton, 
added another interesting experiment to our knowledge of this 
subject. Into a receiver filled with carbonic acid he intro¬ 
duced a bladder two thirds full of coal gas,—when he found 
that the bladder gradually swelled till it became full almost to 
bursting. The carbonic acid had made its way into the blad¬ 
der, while, at the same time, a small quantity of the coal gas 
had escaped into the receiver. Berzelius J explained this ex¬ 
periment on the same principle as those already mentioned. 
The moisture in the bladder becomes saturated with the car¬ 
bonic acid, which it gives off again from the inner surface, when 
it is in contact with the other gas. 
This experiment was repeated with modifications by Baum¬ 
gartner, of Vienna; but it was investigated much more fully by 
Mr. Mitchell §. He employed thin membranes of caoutchouc, 
and found that when a vessel filled with atmospheric air was 
closed with such a membrane, and placed in an atmosphere of 
hydrogen gas, the latter made its way into the vessel till the 
* Poggendorf’s Annalen, x. p. 153. 
f Journal of the Royal Institution , September 1829, p. 74. 
o 
X Arsherdttelse , 1830, p. 54. 
§ Journal of the Royal Institution, N.S. ii. pp. 101, 307. 
